Counterfactual time series analysis for the air pollution during the outbreak of COVID-19 in Wuhan

Environmental issues are becoming one of the main topics of concern for society, and the quality of air is closely linked to people's lives. Previous studies have examined the effects of abrupt interventions on changes in air pollution. For example, researchers used an interrupted time series design to quantify the impact of the 1990 Dublin coal ban; and a regression discontinuity to determine the arbitrary spatial impact of the Huaihe River policy in China. An important feature of each of these studies is that they investigated abrupt and localized changes over relatively short time spans (the Dublin coal ban) and spatial scales (the Huaihe policy). Due to the abrupt nature of these interventions, defining a hypothetical experiment in these studies is straightforward. In response to the novel coronavirus outbreak, China implemented 'the largest quarantine in human history' in Wuhan on January 23, 2020. Similar measures were implemented in other Chinese cities. Since then, the movement of people and associated production and consumption activities have been significantly reduced. This provides us with an unprecedented opportunity to estimate the changes in air pollution brought about by this sudden "silent" move. We speculate that the initiative will lead to a significant reduction in regional air pollution. Thus, we performed counterfactual time series analysis on Wuhan air quality data from 2017-2022 based on three models, SARIMA, LSTM and XGBOOST, and compared the excellence of different models. Finally, we conclude that 'silent' measures will significantly reduce air pollution. Using this conclusion to further investigate the extent of air pollution reduction will help the country to better designate environmental policies.Comment: 9 pages, 8 figure

The Economics of Municipal Solid Waste Management

为减轻大量禽畜废弃物对环境的污染,将其资源化为优质的无害化有机肥料,研究了微生物F468对降低鸡粪N营养元素损失和促进其无害化进程的影响。结果表明,继代80次,F468降低鸡粪氨气挥发的能力无显著变化,能降低鸡粪79%的N元素损失。F468还能通过降低蛔虫卵和粪肠杆菌的数量,促进鸡粪的无害化进程。不添加F468,蛔虫卵和粪肠杆菌达到我国无害化标准（NY884-2004）的时间分别需要25d和20d。加入F468后,蛔虫卵和粪肠杆菌达到我国无害化标准的时间分别需要15d和10d,均比不加微生物提前10d达到我国无害化标准

Human Mobility Trends during the COVID-19 Pandemic in the United States

In March of this year, COVID-19 was declared a pandemic and it continues to threaten public health. This global health crisis imposes limitations on daily movements, which have deteriorated every sector in our society. Understanding public reactions to the virus and the non-pharmaceutical interventions should be of great help to fight COVID-19 in a strategic way. We aim to provide tangible evidence of the human mobility trends by comparing the day-by-day variations across the U.S. Large-scale public mobility at an aggregated level is observed by leveraging mobile device location data and the measures related to social distancing. Our study captures spatial and temporal heterogeneity as well as the sociodemographic variations regarding the pandemic propagation and the non-pharmaceutical interventions. All mobility metrics adapted capture decreased public movements after the national emergency declaration. The population staying home has increased in all states and becomes more stable after the stay-at-home order with a smaller range of fluctuation. There exists overall mobility heterogeneity between the income or population density groups. The public had been taking active responses, voluntarily staying home more, to the in-state confirmed cases while the stay-at-home orders stabilize the variations. The study suggests that the public mobility trends conform with the government message urging to stay home. We anticipate our data-driven analysis offers integrated perspectives and serves as evidence to raise public awareness and, consequently, reinforce the importance of social distancing while assisting policymakers.Comment: 11 pages, 9 figure

Assessment of Past and Present Sediment Quality of Stoney Creek in Burnaby, British Columbia

In analyzing the sediment and water quality of the Stoney Creek habitat, four key aspects were investigated: lithology, sediment/water quality, salmon spawning/incubation, and particle size distribution. The lithology found the streambed sediment layer is 3 cm in depth (over bedrock) and consists mainly of sand and some coarser material including gravels, cobbles, and boulders. The sediment of the offchannel pond is mainly mud (fine material) with a moderate amount of sand and a very small percentage of coarser material including gravels and organic matter (leaf detritus and woody debris). Chemical analysis concluded a significant concentration of iron in the pond environment, with potential for adverse effects to salmon offspring. This report further aims to assess the influences of fine sediment on the quality of salmon spawning habitat and incubation success rate. Permeability of spawning gravels and dissolved oxygen concentrations are measured to see if they support the incubation and growth of salmon eggs. Particle size distributions are found significantly different between upstream pool and pond side. And the difference of particle size distributions can influence salmon production in the off-channel site

Architectural and mobility management designs in internet-based infrastructure wireless mesh networks

Wireless mesh networks (WMNs) have recently emerged to be a cost-effective solution to support large-scale wireless Internet access. They have numerous ap- plications, such as broadband Internet access, building automation, and intelligent transportation systems. One research challenge for Internet-based WMNs is to design efficient mobility management techniques for mobile users to achieve seamless roam- ing. Mobility management includes handoff management and location management. The objective of this research is to design new handoff and location management techniques for Internet-based infrastructure WMNs. Handoff management enables a wireless network to maintain active connections as mobile users move into new service areas. Previous solutions on handoff manage- ment in infrastructure WMNs mainly focus on intra-gateway mobility. New handoff issues involved in inter-gateway mobility in WMNs have not been properly addressed. Hence, a new architectural design is proposed to facilitate inter-gateway handoff man- agement in infrastructure WMNs. The proposed architecture is designed to specifi- cally address the special handoff design challenges in Internet-based WMNs. It can facilitate parallel executions of handoffs from multiple layers, in conjunction with a data caching mechanism which guarantees minimum packet loss during handoffs. Based on the proposed architecture, a Quality of Service (QoS) handoff mechanism is also proposed to achieve QoS requirements for both handoff and existing traffic before and after handoffs in the inter-gateway WMN environment. Location management in wireless networks serves the purpose of tracking mobile users and locating them prior to establishing new communications. Existing location management solutions proposed for single-hop wireless networks cannot be directly applied to Internet-based WMNs. Hence, a dynamic location management framework in Internet-based WMNs is proposed that can guarantee the location management performance and also minimize the protocol overhead. In addition, a novel resilient location area design in Internet-based WMNs is also proposed. The formation of the location areas can adapt to the changes of both paging load and service load so that the tradeoff between paging overhead and mobile device power consumption can be balanced, and at the same time, the required QoS performance of existing traffic is maintained. Therefore, together with the proposed handoff management design, efficient mobility management can be realized in Internet-based infrastructure WMNs

SMURF: Spatial Multi-Representation Fusion for 3D Object Detection with 4D Imaging Radar

The 4D Millimeter wave (mmWave) radar is a promising technology for vehicle sensing due to its cost-effectiveness and operability in adverse weather conditions. However, the adoption of this technology has been hindered by sparsity and noise issues in radar point cloud data. This paper introduces spatial multi-representation fusion (SMURF), a novel approach to 3D object detection using a single 4D imaging radar. SMURF leverages multiple representations of radar detection points, including pillarization and density features of a multi-dimensional Gaussian mixture distribution through kernel density estimation (KDE). KDE effectively mitigates measurement inaccuracy caused by limited angular resolution and multi-path propagation of radar signals. Additionally, KDE helps alleviate point cloud sparsity by capturing density features. Experimental evaluations on View-of-Delft (VoD) and TJ4DRadSet datasets demonstrate the effectiveness and generalization ability of SMURF, outperforming recently proposed 4D imaging radar-based single-representation models. Moreover, while using 4D imaging radar only, SMURF still achieves comparable performance to the state-of-the-art 4D imaging radar and camera fusion-based method, with an increase of 1.22% in the mean average precision on bird's-eye view of TJ4DRadSet dataset and 1.32% in the 3D mean average precision on the entire annotated area of VoD dataset. Our proposed method demonstrates impressive inference time and addresses the challenges of real-time detection, with the inference time no more than 0.05 seconds for most scans on both datasets. This research highlights the benefits of 4D mmWave radar and is a strong benchmark for subsequent works regarding 3D object detection with 4D imaging radar

Stacking up electron-rich and electron-deficient monolayers to achieve extraordinary mid- to far-infrared excitonic absorption: Interlayer excitons in the C3B/C3N bilayer

Our ability to efficiently detect and generate far-infrared (i.e., terahertz) radiation is vital in areas spanning from biomedical imaging to interstellar spectroscopy. Despite decades of intense research, bridging the terahertz gap between electronics and optics remains a major challenge due to the lack of robust materials that can efficiently operate in this frequency range, and two-dimensional (2D) type-II heterostructures may be ideal candidates to fill this gap. Herein, using highly accurate many-body perturbation theory within the GW plus Bethe-Salpeter equation approach, we predict that a type-II heterostructure consisting of an electron rich C3N and an electron deficient C3B monolayers can give rise to extraordinary optical activities in the mid- to far-infrared range. C3N and C3B are two graphene-derived 2D materials that have attracted increasing research attention. Although both C3N and C3B monolayers are moderate gap 2D materials, and they only couple through the rather weak van der Waals interactions, the bilayer heterostructure surprisingly supports extremely bright, low-energy interlayer excitons with large binding energies of 0.2 ~ 0.4 eV, offering an ideal material with interlayer excitonic states for mid-to far-infrared applications at room temperature. We also investigate in detail the properties and formation mechanism of the inter- and intra-layer excitons.Comment: 15 pages, 6 figure